Wheel-blocking arrangement for an excavating machine

ABSTRACT

At least one supporting wheel of a vehicular excavating machine is blocked against rotation in one direction when a spring-loaded pawl pivoted on the machine frame engages a ratchet on the wheel. The pawl is of rectangular shape symmetrical relative to its pivot axis and two of its flat faces engage perpendicular flanks of conforming notches in the ratchet under the pressure of the pawl spring. The spring may be shifted on the pawl to prevent forward or backward rolling of the machine while permitting free rolling movement in the opposite direction.

ilnited Mates Patent 1 352mm [72] Inventor Ernst Menzi 1,783,852 12/1930 McGuire 188/30 Wldnau, Switzerland 1,816,968 8/1931 Greutman et a1 192/43.1 X [21] Appl. No. 860,955 2,134,405 10/1938 Hulshizer 188/82.2 [22] Filed Sept. 25, 1969 2,134,420 10/1938 Smith, Sr. 188/82.2 [45] Patented Nov. 16,1971 2,188,328 1/1940 Anderson, Jr. et al 188/30 [73] Assignee Ernst Menzl AG 2,294,510 9/1942 Nakano 192/43.1 X

Widnau, Switzerland 2,978,081 4/1961 Lundin 192/43.1 [32] Priority Oct. 8, 1968 3,249,185 5/1966 Moorhead l92/43.1 [33] Austria 3,467,231 9/1969 Haznar 192/43.1 [31] A9836/68 Primary Examiner-Jiobert E. Pulfrey Assistant Examiner-Clifford D. Crowder 54 WHEEL-BLOCKING ARRANGEMENT son AN Kelma" and Herman EXCAVATING MACHINE 6 l l 2 D l F1 C a 38 ABSTRACT: At least one supporting wheel of a vehicular ex- [52] [1.5. CI 188/30, cavating machine i mocked against rotation in one direction 188/82.7, 214/138, 37/1 74/577 R. when a spring-loaded pawl pivoted on the machine frame en- [51 Int. Cl 136M 1/06 gages a ratchet on h wheeL The paw] is of rectangular Shape [50] Field of Search 88/821 symmetrical relative to its pivot axis and two of its flat faces m i engage perpendicular flanks of conforming notches in the ratchet under the pressure of the pawl spring. The spring may [56] References Cited be shifted on the pawl to prevent forward or backward rolling UNITED STATES PATENTS of the machine while permitting free rolling movement in the 1,451,803 4/1923 Armstrong 188/30 opposite direction.

PATENTEuuuv 15 um 3. 620.333

INVENTOR. PM 7 Me "1.;

WHEEL-BLOCKING ARRANGEMENT FOR AN EXCAVATHNG MACllillNE This invention relates to improvements in excavating machines in which an excavating tool is mounted on a wheeled frame, and stresses transmitted by the tool during excavation tend to cause rolling movement of the frame on the wheels. More specifically, the invention relates to a blocking arrangement for at least one of the wheels.

The invention will be described hereinbelow with reference to a vehicular excavating machine of the type more fully described in my copending application Ser. No. 794,310, filed on Jan. 27, 1969, now Pat. No. 3,534,877. The excavating machine for which the instant invention is of particular utility has a frame which is supported by soil-engaging feet at one end and by a pair of idler wheels at the other end. A shovel is mounted at the end of an arm pivotally fastened on the frame, and is used for excavating soil and similar applications. Operation of the shovel usually exerts stresses on the machine frame in the direction of its normal vehicular movement. The soilengaging feet absorb these stresses only when adequately loaded in a vertical direction, and it is necessary to provide a brake or other blocking arrangement for the idler wheels.

A primary object of the invention is the provision of a simple and effective blocking mechanism for preventing rolling movement of the apparatus on its supporting wheels in response to stress generated by engagement of the excavating shovel with a material to be excavated.

More specifically, the invention aims at a blocking mechanism capable of reliable operation over extended periods under all practical conditions in which an apparatus of the type described is expected to perform. Such conditions may include immersion of the wheels in water or heavy mud. Moreover, it is usually desirable that the wheels be blocked against rolling movement in one direction only so that the excavating apparatus may be moved along an excavating site in one direction while being secured against movement in the opposite direction under excavating stresses.

With these and other objects in view, as will hereinafter become apparent, the invention provides at least one of the idler wheels with a blocking mechanism consisting of a ratchet member of arcuate shape about the axis of rotation of the wheel and a pawl member movable into and out of a position of locking engagement with the ratchet member, one member, and preferably the ratchet member, being fixedly mounted on the wheel, and the other member being mounted on the frame.

Other features and many of the attendant advantages of this invention will readily be apparent from the following description of a preferred embodiment when considered in connection with the appended drawing in which:

FIG. 1 shows an excavating machine of the invention in fragmentary side elevation; and

FIG. 2 illustrates the device ofFlG. l in plan view and partly in section.

Only as much of the excavating apparatus is shown as is needed for an understanding of this invention, the reader being referred to the aforementioned copending application for a more detailed description of the elements omitted from the instant drawing.

One of the idler wheels is provided with a fixedly attached ratchet plate 1 extending about the rim of the wheel in a plane perpendicular to the axis of rotation of the wheel and cooperating with a pawl 2. The teeth of the ratchet plate 1 are spaced about 15 apart in a circle about the axis of rotation which they face. Their converging flanks 3 are flat, and respective flanks of circumferentially consecutive teeth are perpendicular to each other and define rectangular notches 4 in the ratchet plate, the flanks 3 bounding each notch 4 being symmetrical relative to a plane through the axis of rotation of the wheel and the apex of the notch.

The pawl 2 is an elongated, rectangular metal plate mounted on a pivot pin 5 whose axis is parallel to the axis of wheel rotation and passes through the center of gravity of the pawl, the awl being symmetrical relative to the pivot axis. The pin 5 is mounted between two flange plates 6,6 which are fixedly fastened to a member 7 of the vehicle frame, not otherwise shown.

A helical tension spring 8 biases the pawl 2 into the position of locking engagement with the ratchet plate 1 shown in full lines in FIG. 1 in which the pawl prevents counterclockwise rotation of the wheel while not significantly interfering with clockwise rotation. The spring 8 is tensioned between an eye 9 on the pawl z and an eye 10 on the flange plate 6, the eye 9 being spaced from the pivot axis in the direction of elongation of the pawl 2. If it is desired to bias the pawl 2 for blocking clockwise rotation of the wheel, the spring 9' is hooked into an eye 9 on the pawl spaced from the pivot axis oppositely relative to the eye 9, and into an eye 10 on the flange plate 6.

When it is desired freely to move excavating apparatus forward and backward, the pawl 2 is held against the restraint of the spring 8 in an inactive position remote from the fully drawn engaged position, the inactive position being indicated in FIG. 1 in broken lines. A latch 11 is pivoted between the flange plates 6,6 about an axis extending in a common plane with the axis of wheel rotation and with the pivot axis of the pawl 2. It may be swung manually between a fully drawn inoperative position adjacent the frame member 7 and an operative position shown in broken lines, in which the latch 11 engages a shallow notch in the pawl 2 under the pressure of the biasing spring 8.

The pivot axis of the pawl 2 is selected so that a pair of axially extending, perpendicular faces of the pawl 2 simultaneously engages the two flanks 3 in a notch 4 when the pawl 2 is in either one of its locking positions, a face of the pawl perpendicular to a radius drawn on the pivot axis being common to both pairs. This arrangement has been found to contribute materially to the reliable operation of the apparatus even under unfavorable conditions, and to make the apparatus insensitive to contaminants such as particles of the solid material being excavated. Because of the large contact areas between the pawl and the ratchet plate, the contact pressures are relatively low, and the blocking mechanism has a long useful life practically unaffected by wear of its principal elements.

The illustrated device does not rely on critically close tolerances for operativeness. The annular ratchet plate 1 may be stamped from suitable plate stock without secondary machining, and the pawl may be made from flat bar stock in an equally simple and inexpensive manner. Minor deviations from a strictly rectangular shape of the notches 4 and the pawl 2 tend to be reduced by wear during service.

The illustrated blocking mechanism has been found to prevent rotation of the associated wheel in one direction during excavation while permitting free movement of the apparatus in a direction requiring wheel rotation in the opposite direction, as during travel along excavation sites. if necessary, both idler wheels of an excavating apparatus of the described type may be provided with the illustrated blocking mechanism, and the mechanism is equally applicable to excavating apparatus having more than two wheels which are required to be blocked.

What is claimed is:

1. In a vehicular excavating apparatus having a frame, a plurality of supporting wheels rotatable on said frame about respective axes of rotation, an excavating tool mounted on said frame for engagement with material to be excavated, and blocking means for preventing rolling movement of said frame on said wheels in response to stress generated by said engagement of the excavating tool, the improvement in the blocking means which comprises:

a. an annular ratchet member fixedly and coaxially mounted on one of said wheels and having a plurality of teeth directed toward the axis of rotation of said one wheel,

1. said teeth constituting a plurality of circumferentially adjacent pairs of teeth,

2. the teeth of each pair having respective flanks substantially perpendicular to each other and defining therebetween a notch substantially symmetrical relative to a plane passing through said axis and the bottom of the notch;

b. a pawl member;

c. a pivot means securing said .pawl member to said frame for movement about a pivot axis between a first position and a second position,

said pawl member having a plurality of pairs of engagement faces,

one pair of said engagement faces conformingly engaging respective flanks of a notch in said ratchet member in the first position of said pawl member,

. another pair of said engagement faces conformingly whereby said wheel is blocked against clockwise rotation about said one axis in one of said positions of the pawl member, and against counterclockwise movement in the other position of the pawl member; and

d. yieldably resilient means for biasing said pawl member toward said positions thereof.

2. In an apparatus as set forth in claim 1, said pawl member having a substantially rectangular terminal portion remote from said pivot axis and bounded by three faces jointly constituting said two pairs of faces, said one engagement face being common to said two pairs.

3. in an apparatus as set forth in claim 1, said supporting wheels being idler wheels.

4. In an apparatus as set forth in claim I, said faces and flanks being substantially flat.

5. in an apparatus as set forth in claim I, said yieldably resilient means including a spring member mounted on said frame and fastening means for alternatively fastening said spring member to respective portions of said pawl member oppositely spaced from said pivot axis.

6. In an apparatus as set forth in claim 5, detent means for holding said pawl member remote from said positions,

i t II t 

1. In a vehicular excavating apparatus having a frame, a plurality of supporting wheels rotatable on said frame about respective axes of rotation, an excavating tool mounted on said frame for engagement with material to be excavated, and blocking means for preventing rolling movement of said frame on said wheels in response to stress generated by said engagement of the excavating tool, the improvement in the blocking means which comprises: a. an annular ratchet member fixedly and coaxially mounted on one of said wheels and having a plurality of teeth directed toward the axis of rotation of said one wheel,
 1. said teeth constituting a plurality of circumferentially adjacent pairs of teeth,
 2. the teeth of each pair having respective flanks substantially perpendicular to each other and defining therebetween a notch substantially symmetrical relative to a plane passing through said axis and the bottom of the notch; b. a pawl member; c. a pivot means securing said pawl member to said frame for movement about a pivot axis between a first position and a second position,
 1. said pawl member having a plurality of pairs of engagement faces,
 2. one pair of said engagement faces conformingly engaging respective flanks of a notch in said ratchet member in the first position of said pawl member,
 3. another pair of said engagement faces conformingly engaging respective flanks of a notch in said ratchet member in said second position of said pawl member,
 4. one of the engagement faces of each pair being substantially perpendicular relative to a radius drawn through said one face and said pivot axis,
 5. whereby said wheel is blocked against clockwise rotation about said one axis in one of said positions of the pawl member, and against counterclockwise movement in the other position of the pawl member; and d. yieldably resilient means for biasing said pawl member toward said positions thereof.
 2. the teeth of each pair having respective flanks substantially perpendicular to each other and defining therebetween a notch substantially symmetrical relative to a plane passing through said axis and the bottom of the notch; b. a pawl member; c. a pivot means securing said pawl member to said frame for movement about a pivot axis between a first position and a second position,
 2. one pair of said engagement faces conformingly engaging respective flanks of a notch in said ratchet member in the first position of said pawl member,
 2. In an apparatus as set forth in claim 1, said pawl member having a substantially rectangular terminal portion remote from said pivot axis and bounded by three faces jointly constituting said two pairs of faces, said one engagement face being common to said two pairs.
 3. In an apparatus as set forth in claim 1, said supporting wheels being idler wheels.
 3. another pair of said engagement faces conformingly engaging respective flanks of a notch in said ratchet member in said second position of said pawl member,
 4. one of the engagement faces of each pair being substantially perpendicular relative to a radius drawn through said one face and said pivot axis,
 4. In an apparatus as set forth in claim 1, said faces and flanks being substantially flat.
 5. In an apparatus as set forth in claim 1, said yieldably resilient means including a spring member mounted on said frame and fastening means for alternatively fastening said spring member to respective portions of said pawl member oppositely spaced from said pivot axis.
 5. whereby said wheel is blocked against clockwise rotation about said one axis in one of said positions of the pawl member, and against counterclockwise movement in the other position of the pawl member; and d. yieldably resilient means for biasing said pawl member toward said positions thereof.
 6. In an apparatus as set forth in claim 5, detent means for holding said pawl member remote from said positions. 